Synthesis Of High-performance Polyurethane Waterproof Coating For Railway Road And Bridge

In our country, there has been planed passenger dedicated lines named "four vertical and four horizontals" as well as intercity travel system in the densely populated area.16000km high-speed passenger line will be put into operation in2020as planed. Preparation of high-performance waterproof coating has become urgent problem of the railway construction.In this study, the reaction kinetics of the polyurethane(PU) pre-polymerization are investigated by FTIR. The experimental results showed that the reaction was in accordance of the second-order reaction kinetics while the raw materials for the pre-polymerization are MDI-50and polyether. The activation energy was544J/mol and frequency factor constant was1.23L·(mol·min)-1. The optimum reaction conditions were as follows:the raw materials was polymerized at65℃for0.5h, then warmed at80℃and polymerization was continued for2h.PU waterproof coating and elastomer were synthesized by component A and B, component A was the pre-polymer of PU and component B contained curing agent and modified stuffing. This paper discussed the influence of the content of primary materials to the mechanical properties of PU by mechanic experiments, SEM, TGA and DSC. The results were shown as following.(1) The stoichiometric ratio of isocyanate to active hydrogen containing compounds (R value) had significant impact on the mechanical properties of PU materials. The initial R value indicated the R value of the pre-polymerization, the final R value indicated the R value of the curing reaction. With the increasing of the initial R value, the tensile strength of the PU materials increased first and then decreased, while the elongation at break of the PU materials decreased gradually. The optimum value of the initial R was3.0. With the final R value increased, the tensile strength of the PU materials increased gradually, while the elongation at break of the PU materials increased first and then decreased. The optimum value of the final R was1.1. In addition, with the increasing content of trihydric alcohols, the tensile strength of the PU materials increased first and then decreased, while the elongation at break decreased gradually. The optimum content of trihydric alcohol was50%.(2) With the same stoichiometric ratio, the curing effect of MOCA, TX-2and DMTDA were equivalent. Considerated of cost and environmental factors, DMTDA was the optimum curing agents. The performance of PU can be improved by adding polyols in the component B. Compared with caster oil, polyether YD330N enhanced the mechanical properties of PU materials significantly. When the stoichiometric ratio of DMTDA to YD330N was9:1, the PU materials had the best mechanical properties.(3) In component B, as the content of silica increased, the tensile strength of PU waterproof coating increased first and then decreased, the elongation at break increased first and then decreased. The optimal amount of silica was1%. As the content of montmorillonite(MMT) increased, the tensile strength of PU waterproof coating increased first and then decreased, the elongation at break increased first and then decreased. The optimal amount of MMT was4%. Titanium dioxide had the effects of filling and whitening in PU waterproof coating. According to actual demand, the amount of Titanium dioxide was generally less than0.5%. Among the solvents of xylene, acetone, ethyl acetate, appropriate one is xylene, which made PU waterproof coating performanced the best mechanical properties.The indexes of the PU waterproof coating accroded with the standards of "Temporary Technical Condition of Waterproofing Layer for the Concrete Deck of Railway Bridge".